Electrical measuring system



Sept. so 192.4.

H. NYQUIST ELECTRICAL MEAS'JHING SYSTEM Y Filed Oct. 28 1921.

ATTORNEY Patented sept'. so, 1924.

UNITED STATES OFFICE.

HARRY NYQUIST, OF ELMHURST, NEW YORK, ASSlIGNOR` TO AMERICAN '.llEI-EPHYONE AND TELEGRAPH COMPANY, A CORPORATIONv OF NEW YORK.

" I t ELECTRICAL MEASURING SYSTEM.

Application led October 28. 1921. Serial No. 511,064. 1

I lll-rangementfor determining the magnitude of flutter efi'ect produced in a loaded signaling circuit. adapted for the simultaneous,

transmission -ot telephone and telegraph currents.

When telegrapn impulses are transmitted over a loaded signaling circuit simultaneously with the transmission tliereover of voicecui'rents, an effec-t is produced upon the voice currents which is commonly designated as flatten This eli'ect is produced by the action of the direct current telegraph impulses upon the loading coils. The action which the telegraph impulses produce in the loading coils causes a reaction upon the Vvoice currents traversing the said coils, this reaction tending to diminish the amplitude of the voice waves. This manifests itself in the received voice currents in a momentary diminution in the strength of the. said received current, thereby giving rise to an effectwhich has been designated flutter. l

lt is the oniect of the applicants 1nvention to provide an arrangement for measuring the relative magnitude of flutter effect. l

This invention will be better understood from the following description-when read in connection with the attached drawing, which shows a forni of embodiment of the invention. In the drawing, 1J, represents a. signal transmission circuit adapted for the simultaneous transmission of telephone and teler graph currents, and extending between two stations A and l. Connected to the. line L, at stations A and l are the composite sets X, and X2 respectively. These sets, which are of the well known type. comprise the' induetances 1 and 2 conhccted in series to ground with the condensers :l and 4 respectively. Connected in series with the sides of the line L, are the condeusers 5 andG, which serve to prevent the transmission to the terminal telephone apparatus of -ratus herein represented by the bridge polar any telegraph impulses that might pass by the point at which the telegraph terminal apparatus is connected with the line circuit.. Another shunt path to ground to preventthe ei'ectof telegraph impulses on the terminal telephone apparatus is provided by means of the condensers 7 and 8 in series' to ground with the inductances 9 and 10 re-v spectively. The telegraph terminal appaduplex arrangemcnt`12is connected to the Junction point 11 between the condenser 4 and the inductance 2 of the composite set X,. The arrangement of the composite set X2 is similar to X," and needs no further explanation. rIfhe midpoint of the bridge arms of thel telegraph terminal apparatus is connected with one .of the movable arms of the double pole. double throw Vswitch 13, which when operated to the left, as shown in the figure, is adapted to apply a positive impulse `froin the battery B1 to oneside of the line'L and when operated to the rightA to apply a nega-tive impulsefrom the battery B2 to the same side of the said line.

BridgedA across the line L1 at the station A is a network similar to that shown in Fig. 1 of my copending application, Serial No. 511.003, filedA Oct. 28,1921. As described in the said application, such network is designed to c balanced for a definite fre quency and therefore will not transmit current at that frequency. If, however, other frequencies are applied thereto current will be transmitted through the said bridge -to a receiver 11, connected across opposite terminals of the said Abridge network. The variable 'resistance 15 .will be connected into one of the arms ofthe said bridge network whenever the switch 13 is open, but will be. shortcircuited when the switch' is in the position shown in the figure. Connected effectively 'across the line L1 at the station ll by .ineanscf the transformer 16 is a. source lof sinusoidal oscillations 17, of a predetermined frequency. A bridge polaiduplex telegraph set. 18 is connected with the composite set X2, the midpoint of the bridge arms being connected through the contacts of relay 19 with the tongue 20 of 105 the automatic telegraph sender 21. The tongue of the receivingrelay 22 is adapted to control the operation of the relay 19 in a manner which will hereinafter be Jmade clear. The relay 23, which is controlled by no the operation o'f relay 19 and the automatic sender 21,. is adapted to connect an impedance 24 across the output side of the source of sinusoidal oscillations 17, thereby modulating the said oscillations and producing harmonics necessary in the making of the -flutter measurement.

ing 4through the inductance 2 over the lower side 'of the line Ll through a'corresponding inductanee of the composite set X2, thence through the winding of the receiving relay of the terminal vapparatus 18 to ground, which 'willcause the tongue of the receiving relay to be in the position shown in the drawing.' The circuit ofthe windinfr'of the relay 19 will be open and consequently the relay will notte energized. The automatic sender 21, which is adapted to move the tongue 2O between its contacts, will transmit positive and negative impulses overconductor 25 through the con- `tacts of relay 19 to the midpoint of the bridge arms of the telegraph receiving set, where the current will divlde, part passing through the artificial line to ground and the remainder being transmitted over the lower sideof the line L, through the induetance 2 Ofathe set X1, and through the relay of the set 12 to ground.- imultaneous with the transmission over one side of the line L', of the'telegraphic impulses by the automatic sender, current-of a predetermined frequency will be transmitted from the source 17 over the said line to the bridge network connected at station A. Due to the action of the telegraph impulses upon the loading coils connected with the line L the current arriving at station A from the source 17 will contain not only the fundamental frequency transmitted by the said source, but also harmonics produced by the action of the telegraph impulses upon the loading coils. Further, it will contain frequencies slightly higher and sli htly lower than the fundamental, due to 1no ulating action of the telegraph wave. Since the bridge network at station A is balanced for-thefundamental frequency, current of that frequency will not pass through tothe receiver14, but the harmoni of that frequency caused by the eii'ect of the telegraphic impulses upon the loading coils together with the modulation products will pass through and be detected by the receiver 14.

of the line L, and the telegraph receiving A relay of the set 18, which causes the tongue 22 of therelay to close its contact. -Relay 19 will thereby beenergized by current from the battery B3, thereby moving its armatures from their outer to their inner contacts. With the .tongue of the automatic sender in the position s hown in the drawing, current will flow from the posit-ive battery B, through the winding of relay 23, the inner contact of the right-hand armature of relay 29 to the negative battery B5 thereby -energizing relay 23.

By the operation of relay 23, the impedance 24 will be connected across the source of the sinusoidal oscillations 17, therebyproducing modulation products. The fundamental frequency and its modulation frequencies will be transmitted over the line L1 and will 'be impressed across the network at station A.' The network at station A is no longer balanced for the reason that when the switch 13 is operated toward the right the variable resistance 15 is eifectively connected into one of the arms of the said network. Consequently, the current arriving over the line Ll and impressed across the network at A will be transmitted through the said network to the receiver 14. By varying the magnitude of the resistance 15, the intensity of the sound roduced inthe receiver 14 can be varied. y throwinf the 'switch 13 alternately to the right and5 the left, and by adjusting the resistance 15 the point will be reached where the sound produced in the receiver' 14 for the two positions of the said switch will be approximately of equal intensity. The settingof the variable resistance 15 will then be a measure of the flutter.

Although in the drawing I have shown only the form of balanced network shown in Fig. 1 of'my copending application, Serial No. 511,003, filed Oct. 28, 1921, it is to be magnitude of flutter eiect produced upon,

telephone currents by the lsimultaneous transmission therewith of telegraph impulses over the same loaded line circuit. Since the amplitude of the steady part of a iiuttered wave is -great in comparlson with the un.

' steady part of the same wave,

by balancing steady part of a fluttered mission therethrough to the current investigating apparatus is prevented which greatly increases the accuracy of investigation and measurement-of the unsteady part of the said wave, which are of much smaller amplitude.

Although this invention has been disclosed in a definite form and arrangement of parts, it is to be understood that it is capable of embodiment in other -and different forms without departing from the spirit and scope of the appended claims.

What I claim is:

' 1. In a loaded circuit characterized by the simultaneous transmission of a plurality of currents, 'the method of investigating flutter which consists in suppressing the larger steady part of a fluttered wave and transmitting and investigating the unsteady part of smaller am litude.

2. In a loa. ed circuit characterized by the simultaneous transmission of a plurality ofv currents, the method of investigating flutter which consists in ,suppressing the larger steady platt of .a flattered wave and transmitting t e remaining unsteady part yof the futtered wave, producing and transmitting a standard variable wave, and comparing the unsteady part pf the fluttercd wave to the standard wave.'

3. In a lloaded circuit charactgi-ld by the simultaneous transmission of a plurality of currents, the method of investigating flutter which consists in suppressing the larger steady part of a flattered wave and transmitting the remaining unsteady part, transmitting a standard variable wave produced by varying the output wave generated by the source of the originally fiuttered wave, and comparing the unsteady part of the fluttercd wave to the standard wave.

4. In a loaded circuit characterized by the simultaneous transmissi, of a plurality of currents, the method of! l tvcstigating flutter which consists in suppressing the larger wave and transmitting the remaining unsteady part, transmitting a standard variable -wave produced by varying the output wave generated by the source of the originally fiuttercd wave and obtaining a certain fraction of the larger steady part of said wave, and comparing the said unsteady part ol' the fluttered wave to the standard wave.

5. In a flutter measuringr circuit, the combination with a loaded line circuit adapted for the simultaneous transmission of telephone andtelegraph currents of a source of sinusoidal waves of a definite frequency, a source ol' tclcgraphic impulses, a network connected with the said line circuit balanced for the fundamental frequency of the sinusoidal oscillations, current detectin means connected with the said network, an circuit controlling means associated with the said detecting means wheiieby the source of telegraphic impulses may be caused either to transmit over the said line or to modulate the said sinusoidal oscillations at the source.

6. In a fiutter measuring circuit, the combination with a loaded line circuit of com.

posite sets connected across each end thereof, telegraph transmitting and receiving circuits connected with the said composite sets, a source of sinusoidal oscillations also connected across one end of said loaded-circuit, a VVheatstone bridge network balanced for a definite frequency connected across the other end of the said circuit and having current detecting means connected therewith, and circuit controlling means connected with one of the said telegraph transmitting and receiving circuits -adapted to control the operation of the other of said telegraph transmitting and receiving circuits in such a manner that the' said latter circuit may be caused to transmit telegriph signals over the said line circuit or to mo late the sinusoidalv oscillations at source.

7. In aflutter measuring circuit, the combination with a loaded line circuit adapted for the simultaneous transmission of telephone and telegraph currents of a source of sinusoidal waves of a definite frequency, a source of telegraphic impulses, a current indicating device connected with the line circuit and normally balanced for the funtheir damental frequency transmitted by'the source.

of sinusoidal waves, and means to control. the said source of telegraphic impulses in such a manner that the said latter source may be caused to transmit telegraphie signals ovei' the said line circuit or to modulate the sinusoidal oscillations at their source.

8. In a flutter measuring circuit, the combination with a loaded line circuit of a source of sinusoidal voltage, a source of direct current impulses, a network connected' with the' said line circuit having a current indicating device normally balanced for a particular frequency, and means connected with the said source of sinusoidal voltage and coni rolled by the said source of direct current impulses in such a manner that the sinusoidal voltage wave may be modulated by the said direct current impulses.

In testimony whereof, I have signed my name to this specification this 26th day of October, 1921.

HARRY NYQUIST. 

